Treatment of ores



May 31, 1932. J. E. LITTLE l-:T Al.

TREATMENT OF ORES Filed May 26, 1926 2 Sheets-Sheet 1 MVV i May 31, 1932. 1. E. LITTLEET AL 4 1,860,811

TREATMENT OF4 4@RES Filed May` 26, 1926 2 Sheets-.Sheet 2 BYm/lljuslr ZZ.

Patented May 31, 1932 UNITED STATES Pii'rl-:rrv OFFICE JAMES E. LITTLE, OF BETHLEHEM, AND FRANK O. KICHLNE AND AUGUST EHRGOTT, yOIE' LEBANON, PENNSYLVANIA., ASSIGNORS T BETHLEHEM STEEL COMPANY V TREATMENT OF CRES Application led May 26, 1926. Serial iNo.` 111.879.

This invention relates to a method of dressing ores which `exist in nature in a state ofy subdivision, as for example, earthy terruginous ores, such as limonite and turgite and which have ores of other metals associated with them, as for example chromite. Hitlierto it has not been found practicable to separate these ores by the normal methods well known to ore dressing practice.

Our invention has for an. object aprocess for treating complex ores, in which the individual ore components and the gangue are intimately associated and are in a condition of natural subdivision, in order that said ores may be adapted to normal methods of separation.

Asa specific example of this problem there may be mentioned certain chromiferous iron ores of Cuba, containing about 2% of metallic chromium in the form 'of chromite, which latter'it is desirable to separate as a concentrate for the manufacture of ferro alloys.

In these ores the limonite, turg'ite and gangue constituents, such as alumina, for examp e, are in an earthy or clay-like condition. The chromite, on the other hand is in a` relatively granular or sandy condition, and is also rather brittle.

These chromiferous iron ores have hitherto been submitted to a nodulizing` process, wherein the finely divided material is dried and agglomerated to a conditiog suitable for the `blast furnace; in this manner a chromiferous pig iron vhas been obtained suitable for special purposes. But no satisfactory p rocess has yet been developed whereby the chromite could be separated from the limonite and-the gangue ofthe ore, so as to result in any degree of concentration of the chromium bearing material.

After protracted vexperiments with all the methods of ore separation known in the art, none of which proved successful in the treatment ofthis particular chromiferous iron ore, vwe discovered that a washing process in which. the ore could be subjected to a moderate degree of rubbing or of softened abrasion, but-not of sov violent a character as to break up particles of chromite, is very beneficial to the ore and permits ofa substantial separation of limonite and chromite by normal methods of ore separation. Y

The treatment towards which our. invention is directed is that, which may be obtained by rubbingvthe particles of ore with the fingers under Water in a miners pan, and overflowing the particles of limonite which tend i to disperse i'n the Water, leaving 'the chromite i-n the residue of the pan.4 The effect sought is to'rub and wash ofi the clayey limonite` and similar clayey constituents from the sandy or granular constituents such as chromite, Without substantially eii'ectin the condition of this brittle constituent. arious means may be utilized for reproducing this effect on a practical scale, such as by assing a pul of ore in water through a `balli which the balls or rods are formed of or encased in rubber. Alternatively any suitable means of agitation may be used which will not substantially disintegrate the chromite` particles, as for example agitators having soft or flexible paddles or agitators containing rubber balls or materials ofa similarl flexible` character, the agitated pul being then passed to a classifier or to a hy roseparator for separation of the limonite.v The functions of agitationand classification may likewise be combined in a single apparatus where the nature4 ofthe ore permits, as for example in a classifier of the rake type, but equipped with soft'or flexible raking edges.

In order to illustrate the nature of means suitable for carrying out our process, we show in Figure l a sectional-elevation of a ball mill of conventional type having balls encased in rubber;

In Fig.- 2 a part sectional elevation of a rod mill having rods encased in rubber;

In Fig. 3 a sectional elevation of an agitatlor having rubber balls mixed with the ore p11 p; t

In Fig. 4 a cross section, of the scoop provided in a conventional ball mill;

In -Fi 6 an enlarged section of a portion of the ra e.

or rod mil, in

, i l In Fig. 5 a rake type classifier, having rubi Referring to the drawings, we show in Fig. 1 a ball mill 11 of conventional type having driving ear 13, feed scoop 14, a feed launder 15 an balls encased in rubber 16. vIn Fig. 2, we show a portion of a rod mill 11, having a driving gear 13 and rods encased with rubberl.

As previously set forth, the degree of'attrition effected in these Imills, whether they be loaded with balls orwith rods ismodified by the fact that they are encased in exible material, as for example rubber. Thisprobably results in deadening the effect normally produced by the cascading of the balls (or rods) inthe mill and therefore limits their `infiuence entirely to one of softened abrasion with a. minimum of attrition.

In Fig. 3, we show an apparatus of somewhat difl'erent character to those above described, but susceptible of effecting a similar result. In this figure we show a tank 21 having rotatable agitatingmeans 23, feed launder 24 an overiiow launder 25, a discharge outlet 26 and flexible surfaced balls, as for example rubber balls 27. An apparatus such as that indicated in this figure is of the general character of a clay blunger.

As our process contemplates the steps of gentle abrasion to be followed by normal methods of hydroseparation, it will be obvious that these steps may becombined in one apparatus. We therefore show in Fig. 5 a single-deck rake classifier 30 of well known type having a pl-urality of rakes 31, the edges 32 of which are provided with overhanging strips 33 of rubber, leather, or other material of a similarly flexible character. The working position of the rake mechanism in respect to the tank bottom is adjustable, by

the means normally provided in this type of apparatus. A suitable method of fastening the strips to the edges of the rakes is shown in Fig.

It will be apparent that in this process the aim is not to grind or crush any of the constituents but to rub and simultaneously wash the clayey constituents from the granular or sandy. This we secure by rubbing' with cushioned elements in the presence of excess of water to remove the clayey'from the sandy constituents.

By following the methods outlined above and using apparatus of the general types illustrated in the drawings, we have been able to separate 90% of the ore, as an overflow containing only a small proportion of chromite, from a residue or underflow containing a substantial proportion of chromium and which may be further concentrated.

For example, an ore of the following analysis:

Fe 51.31 Ni 1.34. Cr 2.05 Co .13

treated in the manner described yields an overflow containing 90% of the ore, analyzing Fe 49.95 and Cr .7 7. The residue on drying` and screening shows approximately 20% of plus 4Q mesh and 12% of minusf300 mesh, said plus 40 mesh material being mainly limonite and the remainder containing chromite. recycled through the washing vagitator and hydroseparated, to l further eliminate the coarse limonite, analyzed 38%- of chromium sesquioxide, equivalent to 26% of metallic chromium and 22% of Ferric oxide. The final yieldof chromium bearing residue represents about'31/2% of the originall ore. IThe overiiow solids may be nodulized and used in the blast furnace in the usualmanner. The dried residue is suitable for normal reduction in an electric furnace.

From the above it will be evident that We have devised a process, whereby earthy fer- The whole of this residue when e ruginous ores and the like may now be separated in asubstantial degree from other finely sub-divided ores intimately associated with them. The chromiferous iron ore, above referred to as an example of our process, is `butone of many complex ores which are amenable to this treatment. f l

It will be obvious to those skilled in the art, that our invention is susceptible of various changes and modifications without departing from the spirit thereof and we desire therefore that only such limitations'shallbe placed thereupon as are imposed by the prior art or as are specifically set forth in the appended claim.

Having thus described our invention, what we claim as new and desire to secure by Letters .Patent is:

In a process for treating ores comprising limonite and chromite, the steps of subjecting such ores to substantially freely resilient attritive impacts while in substantially free suspension in liquid, said impacts proportioned 4 to disintegrate the limonite but not the chromite, and separating the so differentially disintegrated ingredients.

In testimony whereof we hereunto aflix our signatures.

JAMES E. LITTLE. lFRANK O. KICHLINE. e

AUGUST EHRGOTT.l 

